Soy as a Menopause Treatment Will Not Reduce Hot Flashes in all Women

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In a recent report published in Menopause: The Journal of The North American Menopause Society, researchers have put together a report about current menopause treatment to clarify the results of basic and clinical research studies on the risk and benefits of soy products for pre-, peri- and postmenopausal women who suffer from the symptoms of menopause. One important point of the report was that soy may not be as beneficial for treating symptoms of menopause involving hot flashes in some women because they do not possess the correct type of gut bacteria.

Hot flashes

Hot flashes are sudden episodes of feeling like you have just opened an oven door and forgot to back away to allow the heat to disperse before getting in close to take out a roast. These episodes last anywhere from 30 seconds to a few minutes and are felt primarily in the head and neck regions. The exact cause of hot flashes is still a mystery to scientists, but it is believed to be a result of biochemical and hormonal fluctuations that are brought about due to declining levels of estrogen in women who are entering menopause. Symptoms of menopause that may accompany hot flashes include changes in mood, personality or behavior, changes in self-image, changes in thinking patterns, sleep disruption and excessive night sweating.

Isoflavones and soy
Isoflavones are plant-derived non-steroidal proteins that bind to estrogen receptors. Isoflavones are believed to exert both estrogenic and anti-estrogenic effects, just as endogenous estrogen does. Interest in isoflavones began from previous reports based on observations that only 10% to 20% of Asian women report ever experiencing hot flashes during menopause. In comparison, the percentage of menopausal North American women experiencing hot flashes is 70% to 80%. Initial speculation behind the disparity posited that there must be a dietary difference that could account for their differences. A connection to a high-soy diet containing isoflavones in Asian diets was soon made with the belief that aging Asian women were protected from the effects of menopause by the estrogen binding properties of isoflavones in soy. The protective properties of soy were hypothesized to match the benefits of typical Western hormone replacement therapies for treating declining estrogen levels.

Studies looking into the various forms of isoflavones in soy determined that one of the more important isoflavones is daidzein—a biochemical that is found in high concentrations in soybeans, soy products, red clover, kudzu and the American groundnut. The importance of daidzein is that it is metabolized in the human gut by bacteria into an active form called S(-)-equol, which has enhanced binding abilities to estrogen receptors. Scientists believe that the S(-)-equol mimics some, but not all, activities of endogenous estrogen. It has been proposed that S(-)-equol therefore alleviates some of the symptoms of menopause caused by decreased estrogen production.

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Clinical trials on menopause symptoms and treatment

Clinical trials of menopausal women given varying doses of soy-derived isoflavones resulted in a significant improvement with a 24% to 64% decrease in the number of hot flashes experienced daily. However, not all clinical trials showed a marked improvement. As it turns out, only about 30% of North American women have the ability to metabolize daidzein into its active S(-)-equol form. This inability to convert daidzein into S(-)-equol is due to the lack of a specific gut bacterium. While the human gut has a diverse natural flora, not everyone possesses the gut bacteria needed to convert daidzein into S(-)-equol.

However, this is not to say that isoflavones do not have other benefits for women who lack the necessary bacteria for S(-)-equol production. In fact, many studies show that isoflavones possess pleiotropic properties that are beneficial not only toward vasomotor symptoms associated with hot flashes, but also with breast and uterus health as well as cardiovascular, skeletal and neural systems.

As described in the report, multiple studies are currently being conducted to determine the efficacy of using non-endogenous isoflavone/S(-)-equol-containing supplements to bypass the bacterial requirement in treating women with the symptoms of menopause.
The final conclusion of the report regarding soy for menopause treatment related to hot flashes is that studies show soy is beneficial and should be used for menopause treatment for symptoms of menopause and other estrogen-related conditions. They state that additional studies are needed to compare the conversion of daidzein to S(-)-equol by intestinal bacteria to determine if women who are S(-)-equol producers derive even greater benefits from soy supplements.

Source: Menopause: The Journal of The North American Menopause Society Vol. 18, No. 7, 2011 DOI: 10.1097/gme.0b013e31821fc8e0 by The North American Menopause Society

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